The present invention relates to a paper wrapper construction for use in conjunction with a smoking article, such as a cigarette. Specifically the paper wrapper of this invention can be used to effectively control the burn rate of the smoking article. The paper wrapper of the present invention comprises cellulosic material which is applied to regions of a base paper web.
It is beneficial to make cigarettes in commercial quantities which will have a reduced burn rate if not drawn on by the smoker but which look, feel, taste and burn like conventional cigarettes when being drawn on by the smoker at normal intervals. It is recognized by those skilled in the art that the wrapper configuration and construction strongly influences these characteristics.
Cigarette wrappers, i.e., papers, have known burn characteristics, including burn rates and static burn capabilities. There have been various attempts to modify the burn characteristics of such wrappers. These attempts have employed a variety of wrapper configurations and constructions.
For example, it is known that the burn characteristics can be modified by adding fillers, coatings, or additives to the papers. Weinert U.S. Pat. No. 4,489,650 refers to a self-extinguishing cigarette in which the interior surface of the wrapper is coated with clay. In Cohn U.S. Pat. No. 4,044,778, the cigarette wrapper referred to includes rings or areas coated with deposits from an alkali silicate solution which renders the wrapper non-burning in the coated areas.
In Adams et al. U.S. Pat. No. 4,889,145, the cigarette wrapper referred to includes an area containing a coating of a porosity reducing composition. The coating is comprised of a non-polymer with a polymer binder. Examples of the non-polymer were given as a fatty alcohol and a fatty acid salt.
Durocher U.S. Pat. No. 4,615,345 refers to another attempt to modify the burn characteristics of wrappers. In Durocher the wrapper is made of a cellulose fiber base which normally does not sustain burning when the wrapper is incorporated into a cigarette. This type of wrapper is treated in selected zones with an alkali metal burn promoter such as the potassium salt of citric acid. It is referred to therein that a cigarette made with a wrapper so treated will smolder without being drawn on by the smoker when in the treated zone but when the treated zone is consumed will extinguish itself unless the cigarette is drawn on by the smoker.
Baker et al. U.S. Pat. No. 4,077,414 also refers to a wrapper with modified burn characteristics. In Baker, a wrapper with inherently high porosity is modified by treating the paper with what was referred to as a "gel-forming" substance so as to produce bands of low porosity regions. The "gel-forming" substances disclosed in Baker were all soluble in water and thus were solutions, as opposed to slurries, when applied to the cigarette paper wrapper.
In addition to modifying wrapper burn characteristics by adding fillers, coatings or burn additives directly to the base paper web, burn characteristics have been shown to be able to be modified by applying to the base paper web a strip or patch of a paper having different characteristics than the base web to be modified. For example, it is shown in co-pending, commonly-assigned U.S. patent application Ser. No. 07/605,402, filed Oct. 30, 1990, that cigarette paper can be modified by applying strips of a different paper at periodically spaced positions across the width of the paper web, so that cigarettes produced from the paper web have periodically spaced circumferential bands on the inside of the paper for modifying the burning characteristics of the paper and the cigarette. One treated paper material suitable for forming the periodically spaced strips is described in Hampl U.S. Pat. No. 4,739,775. However, the wrappers discussed in Hampl were formed by the adhesion of the treated paper material to the base paper web by a process which would be difficult and costly to use for mass production.
As discussed above, various types of cigarette wrapper configurations have been proposed for modifying the burn characteristics of cigarettes. However, these wrappers have various problems and disadvantages. Although the wrappers of Weinert and Cohn produce cigarettes with modified burn characteristics, they do not look, feel, taste and burn like conventional cigarettes when being drawn on by the smoker. Although the wrappers of Durocher solve some of the problems exhibited by the Weinert and Cohn wrappers, Durocher did not disclose a process for making such cigarette wrappers in commercial quantities. In addition, although co-pending application Ser. No. 07/605,402 discloses commercially feasible methods that can produce wrappers with both modified burn characteristics and that look, feel, taste and burn like a conventional cigarette when being drawn on by the smoker, such methods are not the only solutions to the problems discussed. Additionally, the wrappers and coatings referred to in Baker et al. and Adams et al. are not the only types that can potentially modify the burn rate of a cigarette.
Johnson U.S. Pat. No. 4,861,427 refers to a fibrous web product with bacterial cellulose as a surface treatment. In Johnson the bacterial cellulose treatment referred to is applied to the entire web. The resulting coating web is used as printing materials which have gloss, smoothness, ink receptivity and surface strength.
Johnson does not refer to the application of the cellulose to papers in selected portions of the web, i.e., in bands or other patterns, nor does Johnson refer to burn control properties that such an application of bacterial cellulose will impart to the resulting paper. Johnson does not disclose the use of the coated web for cigarette paper.
It would be desirable to provide a paper wrapper for a smoking article that effectively controls the burn rate of the smoking article.
It would also be desirable to provide a paper wrapper for a smoking article that looks, feels, tastes and burns like a conventional cigarette when being drawn on by the smoker.
It would further be desirable to provide a paper wrapper in which burn rate control can be achieved economically with mass-production techniques.